Gas-producing nondetonating composition



May 23, 1939. J. TAYLOR GAS-PRODUCING NONDETONATING COMPOSITION FiledMarch 10, 1936 p/me's E y/or, INVENTOR. M

ATTORNEY Patented May 23, 1939 I UNITED 4 STATES PATENT OFFICEGAS-PRODUCIN G NONDETONATIN COMPOSITION James Taylor, Saltcoats,Ayrshire, Scotland, assignor to Imperial Chemical Industries Limited, acorporation of Great Britain Application March 10, 1936, Serial No.68,143 In Great Britain March 11, 1935 9 Claims. (CI. 5214) The presentinvention relates to gas pressure is not capable of sustaining itsdecomposition at operated devices, for example to mechanical deordinarypressure when heated locally, for exvices such as piston-actuatedmechanism or to ample by means of a fuzee. On the other hand, blastingcartridges of the kind comprising a presa mixture in the same form of 80parts by weight sure-resistant vessel and a pressure-responsive ofammonium nitrate and 12 parts by weight of 5 venting device, and inparticular to new and imcharcoal burns quite easily at ordinary pressureproved charges for such devices. The invention when ignited by a fuzee,the proportion of amrelates in particular to such charges comprisingmonium nitrate in this case being only suflicient compositions in whichammonium nitrate is the to oxidise the carbon to carbon monoxide. The

principal or sole gas producing agent. former composition under pressureshows a 10 When ammonium nitrate is heated to a temgreater liability todetonation than the latter. perature between 160 C. and 260 C.unconfined An object of the present invention is the proand underordinary pressure,adecomposition into vision of improved charges forgas-pressurenitrous oxide and water takes place which, aloperateddevices. Aiurther object of the present 15 though exothermic, requires acontinuous supply invention is the provision of improved blasting 15 ofheat for its maintenance. This reaction is a devices of the kindhereinbefore described. A well-known laboratory method for preparingfurther object of the invention is the provision nitrous oxide, andexperience hasshown that in of improved charges for gas pressureoperated carrying out the preparation anexcessive supply devices, whichcharges include compositions caof heat should be avoided, since theammonium pable of undergoing a self-sustained decomposim nitrate mayotherwise itself detonate. If to amtion without detonation when ignitedwith the monium nitrate there is added a combustible aid of a local andlimited heating element. material, e. g., a carbonaceous material or aAccording to the present invention a charge finely divided metal,capable of undergoing rapid for gas-pressure operated devices of thekind oxidation by the available oxygen of the amdescribed comprises agas-evolving composition 26 monium nitrate, the decomposition of theresultand a non-detonating igniting element insufant mixture is morehighly exothermic than that ficient of itself to efiect any substantialgeneral of the ammonium nitrate alone. Like ammonium, rise in thetemperature of the charge, the said nitrate itself, such mixtures areoften too ingas-evolving composition consisting essentially or 30sensitive to be ignited or to be capable of selflargely of ammoniumnitrate and containing as 80 sustained decomposition merely on localheating sensitiser chromic oxide or a chromium comwhen unconfined, and,on the other hand, some pound adapted to generate the same on heating ofthem at least are still more liable to detonate in the presence of theammonium nitrate, so on heating in a confined space. The sensitivitythat the said gas-evolving composition is capable to ignition and toself-sustained decomposition of undergoing a self-sustaineddecomposition 85 on local heating when unconfined depends on withoutdetonation when ignited locally and at the nature of the combustiblematerial and on ordinary pressure by the said heating element; theproportion thereof relative to the proportion The preferred sensitisingmaterials for use in of ammonium nitrate. When using carbonaceous thecharges of the present invention are amingredients as combustiblematerial the tendency monium or potassium dichromates or chromates. 40is for the sensitivity to increase with an increase but the chromates orpolychromates of other in the proportion of the said carbonaceousmaalkali metals, e. g., sodium, may also be dried, terial from thatresulting in the formation of while lead chromate and chromic chloridehave carbon dioxide to that resulting in the formation also a slightsensitising effect and are included of carbon monoxide. As would beexpected, other without the scope of the invention. It is consid- 45factors come into question such as the state of ered that the activesensitising agent is probably aggregation and consolidation of themixture. freshly prepared chromic oxide since it has been As an exampleof the influence of the proporfound that the sensitising eiiect of thefreshly tion of ammonium nitrate on the ease of igniprepared ashobtained by heating ammonium tion, it may be stated that a solid mixtureof 80 dichromate diminishes after a time. It will be 50 parts by weightof ammonium nitrate and 6 understood that the charge may include inpartsby weight of charcoal, although theoregredients other than ammoniumnitrate which tically a balanced combustible composition in are capableof reacting with suitable chromium which there is suflicient ammoniumnitrate to compounds to generate chromic oxide on heatoxidise the carboncompletely to carbon dioxide, ing. Such ingredients together with saidchromium compounds will be understood to be equivalent to the chromatesor polychromates referred to above.

The proportion of the chromate or polychromate required will not usuallyexceed 20% of the weight of the ammonium nitrate, but in most cases veryconsiderably smaller proportions will be quite suiflcient. It willusually be sufllcient to employ about 1% to of the weight of theammonium nitrate. The charges of the invention are thereforecharacterised by their low ash content.

The gas-evolving compositions used in the present invention arepreferably such that, in the absence of the chromic oxide sensitiser,they are capable of undergoing a self-sustained gasproducingdecomposition without detonation either when confined under pressure andignited with the aid of a local and limited heating element, or whenheated at ordinary pressure sufficiently to cause a substantial andgeneral rise in temperature. Such compositions may contain, in additionto the ammonium nitrate, a proportion of an oxidisable material, forexample combustible carbonaceous materials. Suitable oxidisablematerials are starch, charcoal, peat, woodmeal, plant fibre, natural andartificial resins, waxes, bitumens, hydrocarbons, soaps, fats, oils, andmany other organic materials, less combustible or incombustiblematerials such as formaldehyde polymers, ammonium carbonate andbicarbonate, ammonium oxalate, urea, guanidine and other nitrogenousorganic substances, or even certain inorganic nitrogenous materials suchas hydrazine hydrate. Small proportions of inorganic materials such assilica, china clay, magnesium carbonate, chalk, or the like which aresaid to influence the decomposition of ammonium nitrate may also beincluded if desired.

The sensitising chromium compound is preferably distributed uniformlythroughout the gas evolving composition, and the sensitised material maybe manufactured by admixing the chromium compound with the ammoniumnitrate either before or after the addition to the latter of any otheringredients that may be desired. The admixture is conveniently efiectedby a milling operation.

In the charges of the present invention the sensitised composition isignited with the aid of a local and limited igniting element, 1. e., onewhich is insufficient of itself to effect any substantial general risein the temperature of the charge. The igniting element employed shouldbe nondetonating in character and must be capable of generating a flame,fiash, spark or the like in contact with the gas evolving composition.As examples of such an igniting element there may be mentioned anelectric powder fuse, a safety electric igniter or a small smokelesspowder or cordite charge ignited in turn by a fusehead or pemssion cap.It will be understood that the use of a percussion cap in this mannerfor actuating the flame producing igniter is not equivalent to the useof a detonator and does not involve any risk of detonation of the gasevolving composition.

It will be understood that in using the charges of the presentinvention, the pressure under which the gas is generated will rise veryconsiderably as the decomposition proceeds, but it is a characteristicfeature of the invention that the presence of the sensitising agent doesnot appreciably affect the liability of the composition to detonateunder ordinary conditions. The decomposition of a considerable portionof the charge takes place at a temperature below that at which theunsensitised composition would have required to be heated before itcommenced to decompose. The production of the pressure is thus achievedin a gradual fashion,

According to a particular form of the invention, a blasting devicecomprises a pressure-resistant metal vessel fitted with apressure-responsive venting device and charged in the mannerhereinbefore described with a sensitised ammonium nitrate compositionand with a non-detonating igniter. The igniter may suitably consist ofan electric powder fuse, but igniters of the kind described in Britishspecification No. 431,950 may also be employed. In blasting devices ofthis kind, the proportion of oxidisable material in the ammonium nitratecomposition should preferably be suflic'iently high to ensure that noappreciable proportion of free oxides of nitrogen is formed by thecombustion.

In such blasting devices it is preferred, in general, that theproportions of ammonium nitrate and of oxidisable material shouldbe suchthat little or no carbon monoxide is formed among the combustionproducts. Particularly for safety blasting in fiery or dusty mineshowever, the proportions of ammonium nitrate and oxidisable materialshould be so adjusted that the carbonaceous materials present are burntpractically completely to carbon dioxide and water. Ammonium nitratemixtures of this kind are not usually themselves sufficiently sensitiveto support their combustion at ordinary pressures when ignited with theaid of a local and limited igniting element, and consequently thepresent invention is of particular value in providing suitable chargesfor blasting devices of the kind described.

In preparing compositions for blasting in this manner and especially foruse in fiery or dusty mines, inoombustible materials, for exampleammonium carbonate or bicarbonate or other incombustible materialsyielding a high gas volume on oxidation, are particularly useful asmaterials for reacting with the excess oxygen of the ammonium nitratecomposition. Such materials as ammonium carbonate or bicarbonate, whichare themselves decomposable by heat with the production of gases, maythemselves be introduced in greater quantities than that required forthe oxygen balance, and then serve a useful purpose in contributing tothe pressure developed and in moderating the temperature attained.Moderate quantities may usually be introduced by simple admixture, butwhen it is desired to introduce considerable proportions of suchmaterials, it is often convenient to employ a portion at least of theammonium carbonate or the like in granular form well distributedthroughout the remainder of the composition which may itself be inpowder ployed in conjunction with a non-detonating supporting their owndecomposition when ignited with the aid of a local and limited heatingelement, e. 3., a to 100 grain powder fuse.

When the blasting devices as above described are to be used in fiery ordusty mines it is desirable that any combustible organic ingredientspresent should be rendered incapable of being projected in flamingparticles capable of igniting dangerous atmospheres, in order tominimise the risk of any such ingredients being vented while unconsumedor only partly consumed and still burning or taking fire. Suchfireproofing may be effected by impregnation with fireproofing salts,for example ammonium phosphate or sulphate, sodium tungstate, alum orborax.

According to a further form of the present invention a gas-pressureoperated mechanical device, for example piston actuated mechanism or thelike, includes a suitable gas-generating vessel or container and acharge of a sensitized ammonium nitrate composition and a non-detonatingigniting element as hereinbefore described. In this form of theinvention it is usually desirable that the proportion of oxidisablematerial should not only be suflicient to prevent the formation of freeoxides of nitrogen or other corrosive gases, but also to yield arelatively high proportion of permanent gas. In the oxidation of amaterial composed of carbon and hydrogen and whether or not containing aproportion of oxygen in its composition; complete oxidation to carbondioxide and water yields a smaller volume of permanent gas thanoxidation to carbon monoxide and hydrogen, since in the latter case nodiminution in the volume of the products due to the condensation ofwater vapour would be experienced. In the operation of a mechanicaldevice this may be of some importance, and accordingly it will notusually be desirable to minimise the formation of carbon monoxide as inthe case of blasting.

The invention is further illustrated by the following examples in whichthe parts are parts by weight.

Example 1 100 parts of ammonium nitrate were milled with 6 parts ofammonium dichromate and 6 parts of charcoal in an edge runner mill untilthe ingredients were well distributed, the charcoal being added afterthe ammonium nitrate and ammonium dichromate had been lightly mixed. Theloose powder when made into a loose train deep was found to be capableof supporting its own combustion when ignited at one end by means of afuzee, whereas a composition made in similar fashion containing only theammonium nitrate and the charcoal failed to support its combustion whensimilarly ignited. In order to take up the excess oxygen of the mixtureand provide a further source of gas pressure and reduce the temperatureof combustion somewhat there was further incorporated into thecomposition containing the three ingredients 20 parts of ammoniumbicarbonate. The powder so obtained was still capable of supporting itscombustion when locally ignited. A quantity of the powder was enclosed,together with an igniter consisting of a 100 grain powder fuse, in apressure resisting vessel having a pressure responsive venting device.The so charged device was suitable for non-safety blasting purposes.

Example 2 A mixture of 80 parts ammonium nitrate powder, 8 partspowdered potassium chromate, 2 parts starch and 1 part china clay weremilled together until the ingredients were thoroughly mixed. Into theresulting powder there was stirred one third of its weight of ammoniumbicarbonate granules. The composition was used in a blasting device inthe manner described in Example 1 and the so charged device was suitablefor use in a fiery or dusty mine.

Example 3 A mixture of ammonium nitrate, starch; ammonium dichromate andchina clay in the proportions 80:2:5:1 was milled with a suflicientquantity of water to make a stiii paste for half an hour and then spreadout in layers about A" thick and dried. The dried cake was broken downand sieved, the granules retained on a sieve having 20 meshes to theinch but passing a sieve of 6 meshes to the inch being taken. Thegranulated material was mixed with one third of its weight of ammoniumbicarbonate granulated to about the same size. A charge of 215 gms. ofthe composite mixture were loaded into a pressure resistant steel tubeblasting device having a capacity of 680 cos. and venting at a pressureof 12 tons/sq. in., there being also included an electric powder fusecontaining 100 grains of 'blackpowder as igniting agent. The chargeddevice when tested by firing in a gallery containing 9% methane airmixture or containing coal dust gave no ignition.

Example 4 This example illustrates the use of fireproofed woodmeal. asolution containing 2 parts by weight of ammonium sulphate and 2 partsby weight of diammonium hydrogen phosphate dissolved in as little wateras possible, mixing up the woodmeal with the solution for some hours.The fireproofed woodmeal was then dried, and mixed into a mixture ofammonium nitrate, basic magnesium carbonate and ammonium dichromate inthe proportion of 5 parts woodmeal to '7 parts ammonium nitrate and parteach ammonium dichromate and basic magnesium carbonate. The mixture wasused in a blasting device in the manner described in Example 1, theigniter consisting however of a grain powder fuse. The charged devicewas suitable for use in fiery or dusty mines.

Example 5 7 parts mineral jelly were mixed into a previously preparedmixture of 80 parts ammonium nitrate and 8 parts of ammonium dichromate,and the mixture was pressed into the form of a pellet. This compositionis capable of supporting its own combustion with the evolution of carbondioxide and water vapour and was associated with an igniter consistingof a small silicon saltpetre charge itself ignited by a percussion cap.The resulting charge was suitable for use in gas pressure operatedmechanical devices.

Example 6 A charge as in Example 5 included a composition prepared bypressing into the form of a cartridge a mixture containing 80 partsammonium nitrate; 10 parts bitumen and 5 parts ammonium dichromate.Somewhat slower burning compositions were obtained by using theingredients in the proportions 80:5:5 and 80:2:3 instead of 80:10:5.

10 parts of woodmeal were soaked in Erample 7 Acharge as in Example 5included a composition made by pressing into the form of a rod a mixtureof 80 parts ammonium nitrate, 5 parts paraformaldehyde, and 5 partsammonium dichromate.

In order to disclose this application of my invention more clearly,reference is made to the appended drawing which illustrates a preferredembodiment thereof. It is to be understood, however, that this is doneby way of illustration and is not to be regarded as a limitation uponthe scope of my invention.

Referring to the drawing, the blasting device illustrated comprises astrong steel container. I, provided at one end with a firing head 2separated from the container l by a sealing washer 9 of fiber or othersuitable material such that a seal which is gas-tight at very highpressures is assured. The firing head 2 is provided with electrodes Iand 8, one of which (8) is in metallic connection with the firing head2, while the other electrode (1) is insulated therefrom. The mounting ofthe insulated electrode is such as to allow no gas leakage at pressuresup to about 25 tons per square inch. Terminals l and H are provided forthe electrodes which are used in initiating the cartridge electrically.A protective steel cap 3 having an aperture M for the leads of theterminals from the blasting machine or other suitable source of electricenergy, is screwed on the firing head 2.

The blasting charge l3 comprising any of the gas-generating compositionsin accordance with my invention, for example the composition of Example1, is introduced loosely into the tube in the required amount. On theshoulder of the container remote from the firing head 2 is placed afiber or light sealing washer 6 and a steel bursting disc 5 adapted tobe ruptured at a predetermined and considerable pressure, both of thesedevices being held in position by the hollow screwin cap 4, which ispierced with suitable channels for venting the gases and directing anddistributing the blast. An electric powder fuse or safety igniter i2containing, for example, 30 grains of block powder, is used for ignitionand provided with long leads from the electrodes 6 and l and positionedas shown in the drawing so that the flash is directed toward the firinghead. By so positioning the cap, the tendency of the adjacent charge tobe forced into the plug at the end nearest the cap 4 is overcome.

For convenience, the device has been shown in the upright position, butit will be understood that the charge l3 would only assume this positionif the device were horizontal. In practice, the device may be used inany position so long as there is effective contact between the fuse I2and the charge l3.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

1. In a pressure-operated device, in combination a pressure-resistant,pressure-responsive container, defiagrating ignition means and adefiagrating gas-generating composition capable of undergoingself-sustaining decomposition without detonation, said compositioncomprising ammonium nitrate, a carbonaceous substance which combinesexothermically with oxygen and at least approximately 1% of a substancecomprising at least one member of the group consisting of chromic oxide,alkali metal chromates, ammonium chromate, ammonium dichromate, andalkali metal polychromates.

2. In a pressure-operated device, in combination a pressure-resistant,pressure-responsive container, defiagrating ignition means and adefiagrating gas-generating composition capable of undergoing self-sustaining decomposition without detonation, said compositioncomprising ammonium nitrate, a carbonaceous substance which combinesexothermically with oxygen and from approximately 1 to of a substancecomprising at least one member of the group consisting of chromic oxide,alkali metal chromates, ammonium chromate, ammonium dichromate, andalkali metal polychromates.

3. In a pressure-operated device, in combination a pressure-resistant,pressure-responsive container, defiagrating ignition means and adefiagrating gas-generating composition capable of undergoingself-sustaining decomposition without detonation, said compositioncomprising at least one substance selected from the group consisting ofammonium nitrate, guanidine nitrate, urea nitrate and dicyandiamidinenitrate; a carbonaceous substance which combines exothermically withoxygen, and at least approximately 1% of a sensitizing agent comprisingat least one member of the group consisting of chromic oxide, alkalimetal chromates, ammonium chromate, ammonium dichromate, and alkalimetal polychromates.

4. In a pressure-operated device, in combination a pressure-resistant,pressure-responsive container, defiagrating ignition means and adefiagrating gas-generating composition capable of undergoingself-sustaining decomposition without detonation, said compositioncomprising at least one substance selected from the group consisting ofammonium nitrate, guanidine nitrate, urea nitrate and dicyandiamidinenitrate; a carbonaceous substance which combines exothermically withoxygen, and from 1 to 20% of a sensitizing agent comprising at least onemember of the group consisting of chromic oxide, alkali metal chromates,ammonium chro mate, ammonium dichromate, and alkali metal polychromates.

5. In a pressure-operated device, in combination a pressure-resistant,pressure-responsive container, defiagrating ignition means and adefiagrating gas-generating composition capable of undergoingself-sustaining decomposition Without detonation, said compositioncomprising ammonium nitrate, a carbonaceous material and at least 1% ofammonium dichromate.

6. In a pressure-operated device, in combination a pressure-resistant,pressure-responsive container, defiagrating ignition means and adefiagrating gas-generating composition capable of undergoingself-sustaining decomposition without detonation, said compositioncomprising at least one substance selected from the group consisting ofammonium nitrate, guanidine nitrate, urea nitrate and dicyandiamidinenitrate; a carbonaceous material, and from 1 to 20% of a sensitizingagent comprising at least one member of the group consisting of chromicoxide, alkali metal chromates, ammonium chromate, ammonium dichromate,and alkali metal polychromates.

7. In a pressure-operated device, in combination a pressure-resistant,pressure-responsive container, defiagrating ignition means and adefiagrating gas-generating composition capable of undergoingself-sustaining decomposition without detonation, said compositioncomprising at least one substance selected from the group consisting ofammonium nitrate, guanidine nitrate, urea nitrate and dicyandiamidinenitrate;

' a carbonaceous material, a cooling salt, and from tion capable ofundergoing a self-sustaining decomposition without detonation, saidcomposition comprising at least one substance selected from the groupconsisting of ammonium nitrate, guanidine nitrate, urea nitrate,dicyandiamidine nitrate; a carbonaceous material, and from 1 to 20% of asensitizing agent comprising at least one member of the group consistingof chromic oxide, alkali metal chromates, ammonium chromate, ammoniumdichromate and alkali metal poiychromates.

JAMES TAYLOR.

CERTIFICATE OF CORRECTION.

Patent No. 2,159,251

JAMES TAYLOR it is hereby certified that error appears in the printedspecification of the'abo-ve numbered patent requiring correction asfollows: Page 1, second column, line 15, for the word "without"vreaclwithin; and that the said Letters Patent should be readwith this'correction therein that the same may conform to the record of the casein the Patent Office.

Signed and sealed this 11th day of Jul A. '1). 19 9.

Henry Van Arsdale

